Bio
I am a principal engineer at NVIDIA on the OptiX ray tracing team. My focus is eliminating technical obstacles to the adoption of GPUs for film-quality rendering in visual-effects and feature animation.
I joined Pixar early in my career, where I was the lead developer of the RenderMan shading system. At Pixar I worked on five films including Ratatouille and Wall-E. For many years RenderMan was an industry standard, and my code helped render over 140 feature films.
I later moved to New Zealand to join Weta Digital, where I helped develop the
Manuka renderer.
My primary contributions were a native-code shading language compiler and a
novel shading architecture that moved material evaluation out of the inner
loop of path tracing. My work on the Manuka and RenderMan shading systems was
recognized by a nomination for a Scientific and Technical Academy Award in
2016.
I helped deploy Manuka to production and took an active role in its use on over 30 films at Weta, including Avengers: Infinity War, Avengers: Endgame, The Hobbit, and War for the Planet of the Apes. Manuka rendered both Avatar: The Way of Water and Avatar: Fire and Ash, the latter of which was awarded the Academy Award for Best Visual Effects at the 2025 Oscars.
Production highlight videos
Interests
- Shading languages and rendering.
- Compilers and programming language design.
- Turning research ideas into production software.
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- Advanced program transformations — specialization, vectorization, and related techniques.
- High-performance systems: multithreading, data parallelism, GPU acceleration.
More recently, I’ve been interested in developing robust multi-agent workflows for enterprise-grade software development.
I volunteer as a technical mentor at Lassonde Studios at the University of Utah.
Experience
Principal Engineer, NVIDIA, Aug 2018–present · Salt Lake City
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Lead developer of the OptiX Demand Loading Library: hardware-accelerated sparse textures loaded on demand via CUDA virtual memory, significantly reducing GPU memory requirements and I/O bandwidth.
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Developing LLVM-based compilation techniques for fast GPU machine code generation.
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Addressing technical obstacles to the adoption of GPU rendering in the VFX industry.
Head of Rendering Technology, Weta Digital, Mar 2017–Jul 2018
- Led development of the Manuka renderer, which emphasized high quality shading without sacrificing path tracing performance.
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- Managed the Rendering department, including project management, stakeholder engagement, long-term planning, and production support management.
- Our team contributed to over 30 movies at Weta Digital, including War for the Planet of the Apes, which was nominated for the Academy Award for Best Visual Effects.
- Manuka is the core technology behind the Avatar: Flight of Passage attraction at Walt Disney World.
Senior Researcher, Weta Digital, Apr 2010–Mar 2017
- Developed the Manuka shading system, including an advanced compiler that generates native code from RSL using a unique batch-oriented code generator that ensured high texture and memory locality.
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- Built a RenderMan-compliant front end for the renderer, including RIB parser, rendering and plugin APIs, and hierarchical graphics state.
- Shared leadership responsibilities, including project management.
Senior Graphics Software Architect, Intel Corporation, May 2008–Apr 2010
- Led development of SLX, the shading language for native rendering on Intel’s Larrabee platform.
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- Implemented major compiler components, including parser, typechecker, and code generator.
- Incorporated the LLVM compiler toolkit for analysis and optimization.
- Led a small compiler engineering team using Agile methodologies. Defined milestones, managed estimation and sprint planning, tracked bugs and feature requests, and led testing and documentation efforts.
Senior Graphics Software Engineer, Pixar Animation Studios, May 2002–May 2008
- Lead developer of RenderMan shading system.
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Developed advanced shading language features, including shader objects and co-shaders.
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Redesigned shading system for multi-threaded execution.
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Achieved significant performance improvements by tuning for locality.
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Extensively refactored a large 15-year-old code base.
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In its heyday, this system was employed in the production of over 140 movies by numerous studios.
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Developed next-generation shading language for Grail renderer.
- Designed object-oriented shading framework with inheritance and virtual methods.
- Implemented compiler front-end and intermediate infrastructure.
- Developed various program analyses and optimizations.
U.S. Patent 7,589,719: Fast multi-pass partitioning via priority-based scheduling. Issued Sep. 15, 2009.
Senior Programmer, Zoesis Studios, Sep 1998–Apr 2002
- Developed compiler and run-time system for AI-driven, personality-rich animated characters.
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- Language features included fine-grained multithreading, a RETE-based production system, backtracking, and execution lookahead for animation blending.
OttoAndIris.com: Juried exhibit, SIGGRAPH 2001 Emerging Technologies.
Visiting Lecturer and Researcher, Indiana University, Sep 1996–Aug 1998
- NSF Grant CCR-97-11269: A Staged Compiler Architecture for Dynamic Program Optimization, with R. Kent Dybvig.
Intern, Jet Propulsion Laboratory, 1987
- Ground support software for the Mars Observer spacecraft, including a novel testing framework.
Education
- M.S. Computer Science, Carnegie Mellon University, 1989–1996
- B.S. Computer Science, Cornell University, 1985–1989
Film Credits (IMDb)
| Film | Year | Gross (M) |
|---|---|---|
| Avengers: Endgame | 2019 | $2,799 |
| Avatar: The Way of Water | 2022 | $2,334 |
| Avengers: Infinity War | 2018 | $2,048 |
| Furious 7 | 2015 | $1,515 |
| The Hobbit: An Unexpected Journey | 2012 | $1,017 |
| The Jungle Book | 2016 | $967 |
| The Hobbit: The Battle of the Five Armies | 2014 | $962 |
| The Hobbit: The Desolation of Smaug | 2013 | $959 |
| Batman v Superman: Dawn of Justice | 2016 | $874 |
| Finding Nemo | 2003 | $871 |
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| Guardians of the Galaxy Vol. 2 | 2017 | $864 |
| Dawn of the Planet of the Apes | 2014 | $711 |
| Justice League | 2017 | $658 |
| The Hunger Games: Mockingjay – Part 2 | 2015 | $653 |
| The Incredibles | 2004 | $632 |
| Ratatouille | 2007 | $624 |
| WALL·E | 2008 | $533 |
| War for the Planet of the Apes | 2017 | $491 |
| Rise of the Planet of the Apes | 2011 | $482 |
| Cars | 2006 | $462 |
| Rampage | 2018 | $428 |
| Alita: Battle Angel | 2019 | $405 |
| Independence Day: Resurgence | 2016 | $390 |
| The Adventures of Tintin | 2011 | $374 |
| Maze Runner: The Scorch Trials | 2015 | $312 |
| Maze Runner: The Death Cure | 2018 | $288 |
| Alvin and the Chipmunks: The Road Chip | 2015 | $235 |
| Valerian and the City of a Thousand Planets | 2017 | $226 |
| Central Intelligence | 2016 | $217 |
| Fantastic Four | 2015 | $168 |
| Pete’s Dragon | 2016 | $144 |
| Mortal Engines | 2018 | $84 |
| Krampus | 2015 | $62 |
| Spectral | 2016 | — |
Selected Papers
Fascione, Hanika, Leone, Droske, Schwarzhaupt, Davidovic, Weidlich. Manuka: A batch-shading architecture for spectral path tracing in movie production. ACM Transactions on Graphics, 37, 2018. DOI · PDF
Mark Leone, Peter Lee. Dynamic Specialization in the Fabius System. ACM Computing Surveys, vol. 30, no. 3es, article 23, 1998. DOI · PDF
Peter Lee, Mark Leone. Optimizing ML with Run-Time Code Generation. ACM SIGPLAN PLDI, pp. 137–148, 1996. (Selected for 20 Years of PLDI retrospective, 1999.) DOI · PDF
Pellacini, Vidimče, Lefohn, Mohr, Leone, Warren. Lpics: A Hybrid Hardware-Accelerated Relighting Engine for Computer Cinematography. ACM Transactions on Graphics (SIGGRAPH), vol. 24, no. 3, pp. 464–470, 2005. DOI · PDF
Riffel, Lefohn, Vidimče, Leone, Owens. Mio: Fast Multipass Partitioning via Priority-Based Instruction Scheduling. SIGGRAPH/Eurographics Workshop on Graphics Hardware, pp. 35–44, 2004. DOI · PDF
Selected Projects
OptiX Demand Loading Library — GitHub
Sparse texture streaming for GPU ray tracing. The library maintains a page table that tracks which texture tiles reside in GPU memory; when tiles are missing, page requests are processed on the CPU between kernel launches, loading tiles from disk and transferring them to the GPU.
WeekendCompiler — GitHub
An LLVM-based compiler for a subset of C. Implements a recursive-descent parser, a principled AST with accompanying visitor pattern, and an LLVM IR code generator. Intended as a substantial starting point for anyone building a compiled language on top of LLVM.
Still Frames
The Hobbit: The Battle of the Five Armies (2014) — © Weta Digital
The Jungle Book (2016) — © Weta Digital
Pete's Dragon (2016) — © Weta Digital
The BFG (2016) — © Weta Digital